Low-Odor Catalyst for Isocyanate-Derived Foams and Elastomers

ABSTRACT

Provided herein are catalysts useful in providing foam products which are produced using an organic poly isocyanate as a starting material. A catalyst according to the present invention includes the tris-(hydroxyethyl)methyl ammonium cation, and optionally potassium cation, in combination with a variety of possible counter anions present to maintain charge balance and for compatibility. A catalyst according to the invention is preferably used in conjunction with one or more conventional tertiary amine catalysts in a foam producing process. The foams may be polyurethane foams, polyisocyanurate foams, flexible foams, or elastomeric foams.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to U.S. patent application Ser. No.60/489,985 filed Jul. 24, 2003 which is currently still pending.

TECHNICAL FIELD

The present invention relates to catalyst compositions and foamsproduced using the catalysts in reactive processes which employ one ormore isocyanates as a raw material. More particularly the catalysts arequaternary ammonium compounds useful in the production of polymericfoams and elastomers.

BACKGROUND INFORMATION

A large number of chemical substances have been identified which alterthe curing reaction kinetics in reactive systems that include one ormore organic polyisocyanates as a reactant, in addition to the physicalproperties of the final polymer materials produced, and some of thesesubstances are catalytic in nature. Polyurethanes, polyureas, andpoly-isocyanurates are all materials produced using a polyisocyanate asa reactant, and a survey of the prior art reveals volumes of patents inthe field of polyurethane, polyurea and polyisocyanurate polymers. Forexample, U.S. Pat. No. 3,980,594 describes the trimerization of aromaticisocyanates catalyzed by certain ammonium salts. Quaternary ammoniumsalts or inorganic and organic oxygen acids having pK values for atleast one of the dissociable hydrogen atoms equal to or greater than 2.0in aqueous solution are employed as extremely efficient catalysts fortrimerization of organic isocyanates, particularly aromatic isocyanates,to isocyanurates and for urethane formation. U.S. Pat. No. 4,521,545describes the latent catalyst made from an amine and a alkylating esterof an acid of phosphorous. U.S. Pat. No. 4,582,861 describes the use andsynthesis of N-hydroxyalkyl quaternary ammonium carbonate salt. U.S.Pat. Nos. 4,785,025 and 4,904,629 describe the use and synthesis ofsalts based on TEDA. Thus, quaternary ammonium salts have been known tofunction as catalyzing trimerization of isocyanates at the back end ofthe reaction. Typically, they are made from a starting material oftrimethyl amine, which has a very strong amine odor. These salts mayinclude an anion which may be derived from various acids.

In the polyurethane industry there is a need for a delayed actioncatalyst, i.e. a catalyst that will delay the onset of theisocyanate-polyol reaction (“initiation time”) while not substantiallyaffecting the time to the end of the reaction or final cure, or thatwill yield the same initiation time with a shorter cure time. Theproblem is manifested in the production of polyurethane shoe soles whereit would be desirable if the polyurethane forming composition would notbegin to react until it has essentially filled the mold form while alsoreaching a final cured state in substantially the same or shorter timeperiod to maintain productivity.

Past attempts to solve this problem have centered around taking thestandard amine catalyst, i.e. triethylenediamine, and blocking it withan acid to form the simple amine salt. In theory, this approach shouldwork well but from experimentation it failed to delay the initiationtime as desired without lengthening the cure time. U.S. Pat. No.4,582,861 describes the use and synthesis of N-hydroxyalkyl quaternaryammonium carbonate salt as a remedy to this problem.

SUMMARY OF THE INVENTION

The present invention is directed to a process for producing anelastomer, PIR, or PUR foam product by reaction of an organic isocyanateand a polyol in the presence of a tertiary amine catalyst, and theimprovement according to the invention is effected by conducting thereaction further in the presence of a compound which containstris-(hydroxyethyl)methyl ammonium cation. According to one embodiment,the compound which contains tris-(hydroxyethyl)methyl ammonium cation ispresent in an amount of at least 40% by weight, based on the weight ofthe tertiary amine present in the composition from which the foamproduct is produced. Charge counterbalance for thetris-(hydroxyethyl)methyl ammonium cation in the compound may beprovided by the presence of an ion selected from the group consistingof: hydroxide ion, carbonate ion, bi-carbonate ion, chloride ion,bromide ion, a C₁-C₂₀ carboxylate anion, di-hydrogen phosphate anion,mono-hydrogenphosphate anion, and phosphate anion. According to onealternate embodiment of the invention, the process is conducted in thepresence of any amount of water between about 0.05% and 10.0% by weightbased on the total weight of said polyol present, including everyhundredth percentage therebetween. According to preferred embodiments ofthe invention, the tertiary amine is selected from the group consistingof: N,N,N′-trimethyl-N′-hydroxyethyl-bisaminoethylether;bis-(2-dimethylaminoethyl)ether;N,N,N′,N″,N″-pentamethyl-dipropylenetriamine;N,N-dimethylcyclohexylamine; and pentamethyldiethylenetriamine.According to one alternate embodiment, a process according to theinvention is conducted in the further presence of potassium ion, whereinpotassium is present in any amount between 0.1% and 2.0% by weight basedon the total weight of all the components of the composition from whichthe foam is produced, less the weight of the isocyanate compound(s)employed. According to another alternate embodiment, a process accordingto the invention is conducted in the further presence of one or morematerials known to those skilled in the art falling within the classesof: surfactants, flame retardants, and blowing agents when used in theproduction of polyurethane elastomers or polyurethane foams, as one ofordinary skill recognizes materials as falling within theseclassifications from knowledge of prior art foam compositions ofcommerce and published literature sources, including various publishedpatents and patent applications.

According to another alternate embodiment of the invention there isprovided an aqueous solution comprising tris-(hydroxyethyl)methylammonium cation, water, and a tertiary amine, wherein water is presentin any amount between about 5% and 95% by weight based on the totalweight of the aqueous solution and wherein the tris-(hydroxyethyl)methylammonium cation is present in any amount between about 1% and 50% byweight based on the total weight of the aqueous solution and wherein oneor more tertiary amines are present in any amount between about 2.5 and75% by weight based on the total weight of the aqueous solution. Thetertiary amine in such an aqueous solution may be selected from thegroup consisting of:N,N,N′-trimethyl-N′-hydroxyethyl-bisaminoethylether;bis-(2-dimethylaminoethyl)ether;N,N,N′,N″,N″-pentamethyl-dipropylenetriamine;N,N-dimethylcyclohexylamine; and pentamethyldiethylenetriamine.

A further embodiment of the invention provides a solution comprising atris-(hydroxyethyl)methyl ammonium cation-containing compound whichincludes one or more C₁-C₄₀ carboxylate anions dissolved in an organicsolvent selected from the group consisting of: alcohols having betweenabout 1 and about 20 carbon atoms; ethers having between about 1 andabout 20 carbon atoms; alkylene glycols; and polyalkylene glycols.

DETAILED DESCRIPTION

The present invention is directed at including a particular quaternaryammonium cation as part of the catalyst package used in the curing ofurethane foams and elastomers which improves isocyanate conversion anddecreases the time it takes to complete reaction of the isocyanate withthe reactive components, all while preventing strong ammonia-like odorsin the foam. Advantages of using the materials of the present inventioninclude the fact that conversion of the isocyanate at lower temperaturesoccurs when an appropriate trimerization-promoting catalyst is used tocatalyze the reaction of the isocyanate with itself or othercrosslinkable moieties. The conversion at lower temperatures can in turnshorten the time required of the material to reside in a press, thusenabling faster manufacturing cycle times, improved productivity, andreduced costs. In addition, lower density foam is obtained whentris-(hydroxyethyl)methyl ammonium cation is included in theformulations from which PUR or PIR foams are produced.

A quaternary ammonium salt useful as a co-catalyst according to thepresent invention contains the tris-(hydroxyethyl)methyl ammoniumcation, and also contains an anion for charge neutrality. The structureof tris-(hydroxyethyl)methyl ammonium hydroxide (“THEMAH”) is as shownbelow:

This material may be produced by ethoxylation of methyl-diethanolamineunder normal alkoxylation conditions, and is available from Huntsman LLCof Houston, Tex.

In order to provide materials comprising the tris-(hydroxyethyl)methylammonium cation whose charge balance is maintained by anions other thanhydroxide, a solution of THEMAH may be treated with an acidic substance,in which case the protons from the acidic substance react with thehydroxide ion of THEMAH to yield a molecule of water and thetris-(hydroxyethyl)methyl ammonium salt of the anion of the acidemployed. For example, when THEMAH is neutralized with formic acid,tris-(hydroxyethyl)methyl ammonium formate is afforded. When THEMAH isneutralized with acetic acid, tris-(hydroxyethyl)methyl ammonium acetateis afforded. For example, when THEMAH is neutralized with nitric acid,tris-(hydroxyethyl)methyl ammonium nitrate is afforded. For example,when THEMAH is neutralized with sulfuric acid, tris-(hydroxyethyl)methylammonium sulfate is afforded, and so forth. Thus, one of ordinary skillreadily recognizes that the number of anions which may accompany theTHEMA cation is as vast as the number of acids, including all knownorganic acids and inorganic acids. The stoichiometry of theneutralization between THEMAH and a selected acid, and the simplisticnature of acid/base chemistry means that one of ordinary skill mayeasily produce any desired quantity in any solvent of any compoundcontaining a tris-(hydroxyethyl)methyl ammonium cation and the anion ofan acid selected.

Water and various organic materials are all suitable as solvents inwhich to carry out such neutralization reactions between THEMAH and oneor more acidic substances, including without limitation alcohols havingany number of carbon atoms up to about 20; ethers having any number ofcarbon atoms up to about 20, glycols, glycol ethers, hydrocarbons,ketones, and esters.

A foam formed using a catalyst according to the present invention can beeither a rigid polyisocyanurate (“PIR”) or polyurethane (“PUR”) foam, aflexible foam, and/or an elastomeric foam. One end use application forwhich the catalyst of the present invention is readily adaptable is themanufacture of boardstock foam. In such an employment, the catalystaccording to the present invention assists in converting the excessisocyanate to trimer materials in the foam. A catalyst according to thepresent invention may be referred to as a “back-end cure” catalyst,since it improves on the curing rate and conversion of the material.

Preparation of THEMAH Derivatives

Various compounds comprising a tris-(hydroxyethyl)methyl ammonium cationwere prepared and are specified in Table I below. All samples werepurposefully prepared in diethylene glycol (“DEG”) at such aconcentration that the final DEG content would be about 30 wt. %. Eachsample was prepared by adding 333.3 grams of a 30% aqueous solution ofTHEMAH (containing about 0.55 moles of THEMAH) to a DEG solutioncontaining 0.55 moles equimolar amount of the desired acid to a 1 Lround-bottom flask. The water present in the THEMAH starting materialand the water formed in the reaction was removed from the product usinga Buchi Rotovapor rotary evaporator whose water bath was set to 50° C.

According to a process of the invention, a catalyst according to theinvention may be used in conjunction or combination with any other aminecatalyst known to those skilled in the art to improve on the cure timeand shorten the de-mold time of various polyurethane andpolyisocyanurate foam and elastomer systems. TABLE I Sample No. 1 2 3 45 6 Acid Oleic Formic Decanoic Acetic Formic Formic THEMAH (g) 100 100100 100 200 200 Acid (g) 102.7 16.73 63.22 21.8 63.2 63.2 DEG (g) 68.531.6 51.5 34.8 33.5 33.5 water collected (g) 30 48 72 37 53 100 Analysisof product Alkalinity, meq/g 1.508 3.397 2.074 3.127 2.818 3.249 Water,wt. % 4.67 0.75 0.12 2.9 14.19 1.77

For the neutralization reactions between THEMAH and carboxylic acid forwhich quantities of reactants are listed in table I, the THEMAH and DEGwere added to a 1000 mL 4-neck round-bottom flask. The carboxylic acidwas added slowly to the flask using an addition funnel so that thereaction temperature would not exceed 40° C., and the reaction mixturewas stirred for 2 hours. For sample no. 5, water was removed from theproduct mixture under vacuum distillation conditions (60 mmHg, 80° C.).For sample no. 6, water was removed from the product mixture undervacuum distillation conditions (60 mmHg, 100° C.).

The following example formulations in Table II show the differences inmaterials produced using THEMAH vs. DABCO TMR-2 catalyst. In theseexamples, different levels of water were added to each sample so as tokeep the amount of water present in each of formulations I-VI constant.The reason different amounts of water are added to each of theformulations in Table III is because the THEMAH is present as an aqueoussolution and those samples having more THEMAH initially inherentlycontain more water attendant to that THEMAH (since it all came from thesame stock solution). Hence, addition of these different amounts ofadded water are necessary to maintain a constant water concentration inall samples to render comparisons between the data to be meaningful,i.e., the samples prepared using THEMAH give the same amount of blowingas the examples prepared using DABCO® TMR-2 catalyst. TABLE IIFormulation I II III IV V VI Stepan STEPANOL ®PS-2412 polyol 100 100 100100 100 100 PELCAT ® 9540a cat 4.2 4.2 4.2 4.2 4.2 4.2 PELRON Pel-Sil9900 surfactant 2.0 2.0 2.0 2.0 2.0 2.0 THEMAH 0.25 0.5 0.75 — — — DABCOTMR-2 catalyst — — — 0.25 0.50 0.75 Water 0.375 0.25 0.125 0.5 0.5 0.5Pentane 21 21 21 21 21 21 RUBINATE ® 1850 isocyanate 300 300 300 300 300300 Rise profile Cream time, sec 9 8 8 9 9 9 Top of Cup, sec 23 18 19 2121 19 Gel time, sec 34 26 25 30 30 28 Tack free time, sec 44 39 38 40 3840 Rise time, sec 77 66 64 71 73 66 Firm time, sec 97 94 83 94 94 84Free rise density, g/ml 1.53 1.57 1.65 1.69 1.70 1.74

Thus, foams produced in the presence of THEMAH have lower density thanwhen DABCO TR-52 catalyst is employed. DABCO TR-52 catalyst is generallyregarded by those skilled in the art as a typical good “back-end” curecatalyst. TABLE III COMPONENTS PARTS BY WEIGHT control STEPHAN PS-2352polyol 100 — Goldschmidt B-84PI surfactant 2.0 — 141B 16 — Water 1.0 —RUBINATE ®M (3.96 index) 283.8 — B-component 31.8 g 31.8 A-component(isocyanate) 75.7 g 75.7 PELRON ® 9540A  1.3 g 1.3 THEMAH  0.5 g 0 Creamtime, seconds 11 12 Rise time, sec 62 59 Tack free time, sec 34 26Density, g/ml 2.67 3.12

Alternative and/or additional reactants useful with THEMAH include:Polyester polyols, polyether polyols, 1,4-butane-diol, mannich polyols,sucrose polyols, surfactants, either organic (carbon) or silicon based,potassium salts of any and all organic and inorganic acids, other aminecatalysts, blowing agents such as hydrocarbon, carbon dioxide, FREON®141B, HFC-245FA.

Another experiment was set up to compare the effect of Huntsman'sJEFFCAT® TR-63 catalyst (JEFFCAT® TR-63 is tris-(hydroxyethyl)methylammonium formate) in PIR foam versus not having any JEFFCAT® TR-63catalyst in the foam. We collected ReactFTIR data on the formulations,which is set forth in Table IV below. TABLE IV Sample A C D Rubinate M ®isocyanate 216.59 227.54 230.28 PS 2352 polyol 100.00 100.00 100.00Water 0.75 0.75 0.75 Cyclopentane 20.00 20.00 20.00 B-8443 2.00 2.002.00 Fyrol PCF 10.00 10.00 10.00 JEFFCAT ® Z-110 catalyst 0.70 0.70 0.70PELCAT ® 9540A catalyst 3.00 3.00 3.00 JEFFCAT ®TR-63 catalyst — 2.002.50

We first measured the exotherm of each system. This was done bypremixing the polyol, water, cyclopentane, surfactant, flame retardant,tertiary amine, and potassium salt until a homogenous liquid resulted. Aportion of this mixture was added to a one-quart mixing cup. If JEFFCAT®TR-63 catalyst would be used, as in Examples B and C, then theappropriate amount was added to the cup. The cup would be pre-mixedusing a conventional stirring blade at 3000 RPM for 5 seconds followedby adding the correct amount of isocyanate to the cup. The mixture wouldthen be mixed for 7 seconds using the 3000 RPM mixer. It would then bepoured into a cup which had a thermocouple located in the center of thecup. A data acquisition system was connected to the thermocouple torecord the temperature every second. This data was then used to programthe heated probe on the ReactFTIR instrument. This was repeated for eachcatalyst combination, and the data on temperature profiles is specifiedin FIG. 1.

Each individual exotherm profile was used to program the heated probe onthe FTIR instrument. Before we made a run on the FTIR heated probe, weput an 16-oz paper cup, with a one-inch hole in the bottom of the cup,on top of the heated probe. The paper cup was slid 1 inch below the topof the probe. We then programmed the heated probe with the temperatureprofile that had been collected earlier with the particular formulation.The B-component, with added catalyst, was premixed for 5 seconds using aconventional mixing blade at 3500 rpm. RUBINATE® M isocyanate was thenadded to the cup. When the mixer started to mix the components, the FTIRinstrument was started. The foam was mixed for seven seconds and thenpoured on top of the heated probe such that the liquid covered theprobe's top surface. FTIR data was collected for 600 seconds. Duringthat time, hundreds of spectra were collected while the heated probefollowed the heat profile programmed into it. The FTIR spectra werecollected and analyzed. The top of the peaks were converted into datathat was exported to an excel spreadsheet. The resulting peak profilesfor the isocyanurate peak (1409 cm-1) are shown in FIG. 2. As can beseen in this graph, higher levels of JEFFCAT® TR-63 produce a foamhaving higher amounts of isocyanurate in the foam.

As used in the present specification and the appended claims, the term“organic isocyanate” includes a wide variety of materials recognized bythose skilled in the art as being useful in preparing polyurea andpolyurethane polymer materials. Included within this definition are bothaliphatic and aromatic isocyanates, as well as one or more prepolymersor quasi-prepolymers prepared using such isocyanates as a startingmaterial, as is generally well known in the art. Preferred examples ofaliphatic isocyanates are of the type described in U.S. Pat. No.4,748,192, as well as aliphatic di-isocyanates and, more particularly,the trimerized or the biuretic form of an aliphatic di-isocyanate, suchas hexamethylene di-isocyanate (“HDI”), and the bi-functional monomer ofthe tetraalkyl xylene di-isocyanate, such as the tetramethyl xylenedi-isocyanate. Cyclohexane di-isocyanate is also to be considered auseful aliphatic isocyanate. Other useful aliphatic polyisocyanates aredescribed in U.S. Pat. No. 4,705,814. They include aliphaticdi-isocyanates, for example, alkylene di-isocyanates with 4 to 12 carbonatoms in the alkylene radical, such as 1,12-dodecane di-isocyanate and1,4-tetramethylene di-isocyanate. Also useful are cycloaliphaticdi-isocyanates, such as 1,3 and 1,4-cyclohexane di-isocyanate as well asany mixture of these isomers,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophoronedi-isocyanate); 4,4′-,2,2′- and 2,4′-dicyclohexylmethane di-isocyanate,the corresponding isomer mixtures, and the like.

A wide variety of aromatic polyisocyanates may also be used to form apolymer according to the present invention, and typical aromaticpolyisocyanates include p-phenylene di-isocyanate, polymethylenepolyphenylisocyanate, 2,6-toluene di-isocyanate, dianisidinedi-isocyanate, bitolylene di-isocyanate, naphthalene-1,4-di-isocyanate,bis(4-isocyanatophenyl)methane,bis(3-methyl-3-iso-cyanatophenyl)methane,bis(3-methyl-4-isocyanatophenyl)methane, and 4,4′-diphenylpropanedi-isocyanate, as well as MDI-based quasi-prepolymers such as thoseavailable commercially as RUBINATE® 9480, RUBINATE® 9484, and RUBINATE®9495 from Huntsman International, LLC. Other aromatic polyisocyanatesused in the practice of the invention are methylene-bridged polyphenylpolyisocyanate mixtures which have a functionality of from about 2 toabout 4. These latter isocyanate compounds are generally produced by thephosgenation of corresponding methylene bridged polyphenyl polyamines,which are conventionally produced by the reaction of formaldehyde andprimary aromatic amines, such as aniline, in the presence ofhydrochloric acid and/or other acidic catalysts. Known processes forpreparing polyamines and corresponding methylene-bridged polyphenylpolyisocyanates therefrom are described in the literature and in manypatents, for example, U.S. Pat. Nos. 2,683,730; 2,950,263; 3,012,008;3,344,162 and 3,362,979. Usually methylene-bridged polyphenylpolyisocyanate mixtures contain about 20 to about 100 weight percentmethylene di-phenyl-di-isocyanate isomers, with the remainder beingpolymethylene polyphenyl di-isocyanates having higher functionalitiesand higher molecular weights. Typical of these are polyphenylpolyisocyanate mixtures containing about 20 to about 100 weight percentdi-phenyl-di-isocyanate isomers, of which about 20 to about 95 weightpercent thereof is the 4,4′-isomer with the remainder beingpolymethylene polyphenyl polyisocyanates of higher molecular weight andfunctionality that have an average functionality of from about 2.1 toabout 3.5. These isocyanate mixtures are known, commercially availablematerials and can be prepared by the process described in U.S. Pat. No.3,362,979. The present invention includes the use of mixtures of isomersof isocyanates, which are produced simultaneously in a phosgenationreaction, or any blend of two or more isocyanates (including two or moremixtures of isocyanates, or a single isocyanate with a mixture ofisocyanates) which are produced using two or more separatephosgenations. One preferred aromatic polyisocyanate is methylenebis(4-phenylisocyanate) or “MDI”. Pure MDI, quasi-prepolymers of MDI,modified pure MDI, etc. are useful to prepare materials according to theinvention. Since pure MDI is a solid and, thus, often inconvenient touse, liquid products based on MDI or methylene bis(4-phenylisocyanate)are also useful herein. U.S. Pat. No. 3,394,164 describes a liquid MDIproduct. More generally, uretonimine modified pure MDI is included also.This product is made by heating pure distilled MDI in the presence of acatalyst. The liquid product is a mixture of pure MDI and modified MDI.The term organic isocyanate also includes quasi-prepolymers ofisocyanates or polyisocyanates with active hydrogen containingmaterials. Any of the isocyanates mentioned above may be used as theorganic isocyanate component in the present invention, either alone orin combination with other aforementioned isocyanates.

Consideration must be given to the fact that although this invention hasbeen described and disclosed in relation to certain preferredembodiments, obvious equivalent modifications and alterations thereofwill become apparent to one of ordinary skill in this art upon readingand understanding this specification and the claims appended hereto. Thepresent disclosure includes the subject matter defined by anycombination of any one of the various claims appended hereto with anyone or more of the remaining claims, including the incorporation of thefeatures and/or limitations of any dependent claim, singly or incombination with features and/or limitations of any one or more of theother dependent claims, with features and/or limitations of any one ormore of the independent claims, with the remaining dependent claims intheir original text being read and applied to any independent claim somodified. This also includes combination of the features and/orlimitations of one or more of the independent claims with the featuresand/or limitations of another independent claim to arrive at a modifiedindependent claim, with the remaining dependent claims in their originaltext being read and applied to any independent claim so modified.Accordingly, the presently disclosed invention is intended to cover allsuch modifications and alterations.

1) In a process for producing an elastomer, a PIR, or PUR foam productby reaction of an organic isocyanate and a polyol in the presence of atertiary amine catalyst, wherein the improvement comprises conductingthe reaction in the further presence of a compound which containstris-(hydroxyethyl)methyl ammonium cation, said compound being presentin an amount of at least 40% by weight, based on the weight of thetertiary amine present in the composition from which said foam productis produced. 2) A process according to claim 1 wherein the chargecounterbalance for said tris-(hydroxyethyl)methyl ammonium cation isprovided by the presence of an ion selected from the group consistingof: hydroxide ion, carbonate ion, bi-carbonate ion, chloride ion,bromide ion, a C₁-C₄₀ carboxylate anion, dihydrogen phosphate anion,mono-hydrogenphosphate anion, and phosphate anion. 3) A processaccording to claim 1 wherein said process is conducted in the presenceof any amount of water between about 0.05% and 50.0% by weight based onthe total weight of said polyol present. 4) A process according to claim1 wherein said tertiary amine is selected from the group consisting of:N,N,N′-trimethyl-N′-hydroxyethyl-bisaminoethylether;bis-(2-dimethylaminoethyl)ether;N,N,N′,N″,N″-pentamethyl-dipropylenetriamine;N,N-dimethylcyclohexylamine; and pentamethyldiethylenetriamine. 5) Aprocess according to claim 1 which is conducted in the further presenceof potassium ion, present in any amount between 0.05% and 4.0% byweight, based on the total weight of the foam produced. 6) A processaccording to claim 1 which is conducted in the further presence of oneor more materials known to those skilled in the art falling within theclasses of: surfactants, flame retardants, and blowing agents when usedin the production of polyurethane elastomers or polyurethane foams. 7)An aqueous solution comprising tris-(hydroxyethyl)methyl ammoniumcation, water, and a tertiary amine. 8) An aqueous solution according toclaim 7 wherein said tertiary amine is selected from the groupconsisting of: N,N,N′-trimethyl-N′-hydroxyethyl-bisaminoethylether;bis-(2-dimethylaminoethyl)ether;N,N,N′,N″,N″-pentamethyl-dipropylenetriamine;N,N-dimethylcyclohexylamine; and pentamethyldiethylenetriamine. 9) Asolution comprising tris-(hydroxyethyl)methyl ammonium cation and one ormore C₁-C₄₀ carboxylate anions dissolved in an organic solvent selectedfrom the group consisting of: alcohols having between about 1 and about20 carbon atoms; ethers having between about 1 and about 20 carbonatoms; alkylene glycols; polyalkylene glycols; glycol ethers;hydrocarbons; ketones; and esters.